NUMERICAL ANALYSIS OF TWIN TUNNELS USING PLAXIS 2D

Abstract

The advancement in urban transport necessitates the creation of dual or new singular tunnels in conjunction with the pre-existing ones. The impact of the twin tunnel location and construction method on soil displacement and the resultant forces exerted on the tunnel lining necessitates a thorough investigation of these factors in relation to tunnel design. The objective of this study is to construct a two-dimensional computational model for the purpose of examining the effects of dual tunnels on the adjacent soil and the tunnel lining. The significance of this lies in the fact that the interaction between the twin tunnels has the potential to induce considerable ground deformation, thereby presenting a potential hazard to structures in close proximity. The research conducted a comparative analysis of the impact of tunnel dimensions, depth of soil covering, and distance between tunnels, on the stability of the surrounding soil and the tunnel lining. The circular and horseshoe tunnel shapes were utilised in the study, which was conducted in geologically weak rock formations. This study examined the impact of various tunnel shapes on ground deformation and forces, including bending moment, axial force, and shear force, in the lining of the tunnel. A comparative analysis was conducted utilising a jointed rock model within the Plaxis 2D software. The findings of this study suggest that circular tunnels exhibit greater settlement in comparison to both horseshoe and rectangular tunnels. Moreover, increasing the dimensions of tunnels while maintaining a constant centre-to-centre distance for both circular and horseshoe shaped tunnels led to an increase in ground settlement and forces within the tunnel lining. As the overburden increased, the maximum settlement value and forces in the tunnel lining for circular tunnels decreased. The study reveals that in horseshoe-shaped tunnels, there is a decrease in the maximum ground settlement values, whereas the forces in tunnel linings increase with the increase in the overburden. The research findings indicate that an increase in tunnel spacing, for both circular and horseshoe tunnels, resulted in a reduction of ground settlement and forces in the tunnel lining.